CMF / CRF Details

CMF ID: 7979

Install a traffic signal and left turn lanes

Description: Install a traffic signal and left turn lanes

Prior Condition:  Intersections with a stop sign on minor roads

Category: Intersection traffic control

Study: Safety Evaluation of Signal Installation With and Without Left Turn Lanes on Two Lane Roads in Rural and Suburban Areas, Srinivasan et al., 2014

Star Quality Rating:4 Stars  [View score details]
Rating Points Total:120
Crash Modification Factor (CMF)
Adjusted Standard Error:
Unadjusted Standard Error:0.028
Crash Reduction Factor (CRF)
Value:57.6  (This value indicates a decrease in crashes)
Adjusted Standard Error:
Unadjusted Standard Error:2.8
Crash Type:Other
Crash Severity:All
Roadway Types:Not specified
Street Type:
Minimum Number of Lanes:2
Maximum Number of Lanes:2
Number of Lanes Direction:
Number of Lanes Comment:
Crash Weather:Not specified
Road Division Type:
Minimum Speed Limit:
Maximum Speed Limit:
Speed Unit:
Speed Limit Comment:
Area Type:All
Traffic Volume:
Average Traffic Volume:
Time of Day:All
If countermeasure is intersection-based
Intersection Type:Not specified
Intersection Geometry:4-leg
Traffic Control:Stop-controlled
Major Road Traffic Volume:Minimum of 1360 to Maximum of 15500 Annual Average Daily Traffic (AADT)
Minor Road Traffic Volume:Minimum of 1036 to Maximum of 8884 Annual Average Daily Traffic (AADT)
Average Major Road Volume :8555 Annual Average Daily Traffic (AADT)
Average Minor Road Volume :3997 Annual Average Daily Traffic (AADT)
Development Details
Date Range of Data Used:1992 to 2012
Type of Methodology Used:Before/after using empirical Bayes or full Bayes
Sample Size (crashes):762 crashes before, 310 crashes after
Sample Size (sites):48 sites before, 48 sites after
Sample Size (site-years):238 site-years before, 228 site-years after
Other Details
Included in Highway Safety Manual?No
Date Added to Clearinghouse:Nov 10, 2016
Comments:The CMF was developed for both rural and suburban areas. CMF applies to frontal impact crashes, including 1) left turn same roadway, 2) left turn different roadway, 3) angle, 4) right turn same roadway, 5) right turn different roadway, 6) sideswipe, and 7) head-on.